This invention relates to a solar energy collector. More particularly, this invention relates to a flat plate collector having improved collection capabilities.
Flat plate solar energy collectors are well known in the art. Generally, they comprise a flat black collector surface spaced apart from a sheet of glass; the back surface is insulated to prevent heat loss. Solar radiation passes through the glass to the collector surface where it is absorbed and transformed to thermal energy. However, the "black" collector surface, while absorbing almost 100% of the incident solar radiation, suffers from the disadvantage that it emits in the infrared spectrum nearly 100% of the black body radiation corresponding to the temperature of the collector surface.
In order to obviate energy losses through emission, some prior art researchers advocate the use of "selective" collector surfaces. However, while such surfaces lower emission to about 10%, they absorb at best, only about 90% of the incident solar radiation. They may be expensive to apply and, in some cases, display instability under conditions encountered in use.